The present invention relates to a method for adapting and implanting at least one dental porcelain chip in a cavity, in which the cavity and each porcelain chip is subjected to necessary etching, silanisation, and application of a binder before implantation takes place.
Characteristically, existing methods for placing fillings which are inexpensive to the patients are also technically/medically unsatisfactory, whereas methods providing qualitatively satisfactory results are very expensive. Now, a new method is proposed which provides optimal results to the patients at relatively reasonable costs.
Today there are two kinds of "filler materials". One kind consists of the plastic materials (amalgam, composites, and glassionomeric cement), which have the property of curing in the mouth. This group of fillers is inexpensive, but each material is separately connected with essential disadvantages. The other main group is prepared outside the mouth, before cementation in the mouth occurs. The point of this new method is to combine use of the main groups in such a manner that the advantages of both groups are achieved, at the same time as disadvantages are minimized.
In order to describe the present situation it should be mentioned that amalgam is a strong and inexpensive material, but it is aesthetically unsatisfactory and contains large amounts of mercury. It is, thus, on its way out now.
Composites (plastic fillers) are unsuitable in the molar area, and are not particularly suitable in the premolar areas (i.e. teeth behind the canine teeth). The load in these areas will readily cause fillings to crack and be prone to scaling. During the curing process the material, furthermore, is deformed with a consequent hazard of due to cracking injuries of the teeth as well as damage to the nerves.
Glassionomeric fillings are not very durable in areas with high loads.
Gold inlays are qualitatively first class, but often aestethically unsatisfactory, and they are also labour intensive and very expensive.
Composites may be manufactured by a dental technician in stead of being provided to form fillings. Most of the above mentioned disadvantages of composites may, in that case, be avoided, but the inlays still readily crack. Manufacture by a dental technician is also considerably more expensive.
Porcelain inlays or inserts which are manufactured by a dental technician may readily show porosities and may thus break. The laboratories of dental technicians do not permit manufacture of porcelain under optimal conditions of pressure and temperature. Also, porcelain inlays manufactured by technichians are very expensive.
Prefabricated or industrially produced porcelain is considerably stronger than the porcelain inlays, which may be manufactured in the technichian's laboratories. A recently developed system, the so called CAD-CAM, is based on fitting prefabricated porcelain blocks. The (only) CAD-CAM system on the market is introduced by Siemens and designated Cerec. This system is characterized by the fact that the porcelain inlay is grind fitted by the dentist by the aid of a machine. The system has the essential advantage that the inlay can be completed in one operation, and that it is unnecessary to involve a technichian. The result is a very robust porcelain filling. A disadvantage of the system is that it is initially very cost intensive. At present the system requires an investment of approximately NOK 300 000. Additionally, there are costs of material in the order of NOK 100 for each insert. Also, use of the system is quite complicated. Before the dentist manufactures an inlay, the preparation (excavation) must be photographed three-dimensionally by the aid of a special video camera. Photography requires optimal conditions and it may be difficult to achieve a useful result. It is necessary to screen the area by rubber dam (a special plastic mask), and to spray the tooth with a special powder to permit the camera to record shapes and differences of height. After photography an image of the tooth is displayed on a display unit. The dentist then draws the inlay proper on the display unit. Such drawing may seem complicated to many dentists.
As mentioned above, fitting of the inlay is carried out by the aid of a machine, which shows considerable technical limitations and thus, cannot fit all kinds of inlays. Before the inlay is cemented, it must be adapted to the tooth. It may be necessary to fit inside the inlay to get the inlay in place. Also, it must be adapted to the adjacent teeth. It is impossible to photograph the tooth and adjacent teeth in such a manner that one may draw the correct approximal relations (relation/points of contact with adjacent teeth) directly. In some cases it may also be very difficult to place the camera correctly, because clamps keeping the rubber dam in place may constitute an obstruction. This is in particular the case with the rearmost teeth. As regards the latter, it will always be difficult to provide a satisfactory inlay. For completeness it should be mentioned that it is not possible to achieve an optimal adaptation to the tooth. Between the inlay and tooth a crack is formed, which has to be filled with cement (composite). This, however, does not represent any significant disadvantage.
The CAD-CAM (Cerec-system) represents an substantial new development in the dental technical art. As will appear from the description above, the system is, however, relatively expensive in use. Also, it is complicated, labour intensive, and it has limitations as to applicability.
Before the new method is disclosed, cementation of Cerec-inlays should be described in more detail, because it shows points of resemblance with the proposed method.
When the Cerec-machine has completed preparation of the inlay, approximal relations must at first be adapted (i.e. adapted to adjacent teeth).
Then the porcelain inlay must be treated in a special manner to be able to bond to the composite. Etching with hydrofluoric acid is carried out to roughen the surface. Silanisation follows and a "bonding" or binder is put on and cured. This "bonding" bonds to the composite. Before photography, glassionomic cement is placed in the pulpal portion (bottom of the tooth) to protect the tooth and to prevent the nerve from dying. Cement is also used to align uneveness. Then, the enamel of the tooth is etched with phosphoric acid to be roughened. Then, a thin layer of "bonding" is blown into all uneven portions. The inlay may then be cemented by the aid of composite. At present, this is used by most dentists to cure composite. Finally, the inlay is fitted to the desired level and is polished.